Roasting process



July 30, 1940.

T. R. HAGLUND ROASTING:v PROGESS Filed Oct. 26, 1937 @ecol/ffy lgf.

Patented July 30, 1940 PATENT vOFFICE `v 2,209,331 VaoAs'rIfNc. raocassTure Robert Haglund,` Stockholm, Sweden Application october ze, 1937,serial No. 171,177

' In Sweden November 12, 1936 14 Claims.

The present invention relates to processes for roasting or roasting andsmelting of materials containing sulphides, such as sulphides andsulphide-ores. AThe processes are particularly adapted to the winning ofthe sulphur content of these materials in the form of free sulphur or asacomponent of a gas having a high content of sulphur dioxide.

In the present processes for the roasting of sulphides and sulphide-oresa high content of nely divided particles will easily vcause a sinteringof the sulphide material to form lumps, which makes a control of theroasting procedure highly dilcult. When sulphide-ores are treated -inshaft-furnacesvit has also been difficult to use a charge having largerpercentages of nely divided sulphide. These circumstances must naturallybe regarded as a drawback in view of the fact, that the tendency is toemploy flotation 2o -processes to an increasing degree for the workingup of sulphide-ores, which processes as a.

and smelting of other finely divided or finely' comminuted sulphides,mattes, and sulphideores.

According to the present invention the roasting of the sulphide materialis effected by dispersing the iinely divided sulphide material in anoxidizing stream of gas preferably consisting of oxygen or air enrichedwith oxygen. After the roasting, the material is either collected in asolid state or in the form of a molten bath. The amount of free oxygensupplied by the oxidizing gas may be so adjusted that the free oxygen isconsumed without oxidizing more than part of the sulphur content of thesulphide material into SO2. The temperature is, according to oneembodiment of the invention, raised to such a level that the sulphide ofiron melts while in suspension. As soon as the free oxygen has beenconsumed by the formation of SO2, the iron sulphide reacts to aconsiderable degree with the SO2 under formation of free sulphur andoxide of iron. The oxidized particles may be separated from the gas inthe form of a molten bath. In .3 order to facilitate this separation thevelocity of (Cl. I5-9) v the gas is kept very low by employing anoxidizing gas with a considerably higher content of oxygen than thatcontained in ordinary air. 'I'his also means a more intensifiedevolution of heat, which is necessary to produce fusion of the dilcultlymelting oxide particles. The amount of the oxidizing gas may be adjustedso that only part of the sulphur content is converted into SO2, but incertain cases the amount of oxygen may, for the purpose of intensifyingthe development of heat, be increased so that all or nearly all thesulphur in the resulting gas is obtained aS S02.

By an adjustment of the temperature conditions during the roasting inthe described manner the advantage is i. a. obtained that a morecomplete oxidation will be effected in shorter time than otherwise ispossible, even when working with a deficiency or only a slight excess ofthe oxidizing agent. It is in this way possible to obtain a gas which isricher in SO2 than that which is usually obtained, for which' reason theutilization of the gas e.` g. for thev recovery ofvsulphur may be mademore economical. It has further been discovered that at temperatureshigher than that at which melting of iron sulphide occurs, an oxidationof iron sulphide by SO2 with the formation of oxide of iron and freegaseous sulphur will take place. It is thus possible, by using asuitably adjusted amount of oxygen in the reaction, tocause the reactionto proceed in such a direction that SO2 which is rst formed will, atleast partly, react with iron sulphide to form free sulphur. 'I'hisoxidation may, if desired, also be carried out by means of extrasupplied SOz.

In order to obtain the high temperature which is characteristic for thereaction process according to the invention, it is advisable toupreheatthe gas to be used for the oxidation. The sulphide material may also besubjected to a preheating prior to its dispersing in the gas stream. Thetemperature may likewise be regulated by supplying and burning one orseveral additional combustible substances such as powdered coal, fueloil, sulphur, carbon monoxide gas, etc. The supply of such additionalcombustibles is in many cases of great importance for attaining thetemperature which is necessary for an initiating of the reaction processbetween the oxidizing gas and the sulphide material. The composition ofthe employed oxidizing gas is of particular importance for the reactionprocess. Although this gas, in certain cases when the products ofoxidation are not separated in form of a molten bath,

A this showing,

may consist of air, use is preferably made of oxygen gas or air enrichedwith omen, in which latter case a high enrichment of the omen as a ruleis preferable. By the use of oxygen or air highly enriched with oxygeninstead of ordinary air, the following advantages are i. a.. obtained.The temperature at which the sulphide material will begin to oxidizewill be lower than if air is used. Heat liberated in the oxidationprocess will not, or at least only to considerably less dearee be usedfor the heating of nitrogen, which constitutes the major part ofordinary air, and may therefore be better utilized for producing thedesired temperature of the components taking part in the reactionprocesses, as well as of the products formed. The temperature conditionsmay e. g. in this way be easily controlled in such directicm that acomplete melting of the material under treatment will take place. Since,furthermore, the volume of gas may be kept at only a fraction of thatwhich is obtained when the oxidation is made by means of air, it ispossible to separate at least a considerable part of the moltenparticles from the gas stream and to collect them in the form of amolten bath. It is possible to obtain a gas in the roasting having avery high content of S02, which thus i. a. may be used to greatadvantage for the production of free sulphur by a reduction of S02, e.g. ac cording to processes known per se. It is also possible to controlthe oxidation process when roasting sulphides of iron in such a mannerthat at least a considerable percentage of the sulphur content of thesulphides will be directly recovered as free .sulphur and as a componentof a gas having a high content of sulphur.

My invention can be described in more detail by reference to theaccompanying drawing which shows, in the form of now sheets, twoembodiments of my process, wherein a sulphide ore is roasted with theproduction of free sulphur. In

Fig. l represents a reaction in which a suspension of a sulphide oremoves downwardly through three reaction zones and in parallel with aflow of oxidizing gases, while Fig. 2 represents a process in which thesuspended particles of sulphide ore move downwardly in a tower incounter-current to a stream of gases which ascend the tower.

The two gures are provided with descriptive legends which are believedto make the respective processes represented therein immediatelyevident. In Fig. 1 the ore is introduced into Stage A in the form of asuspension at the top of the figure, together with oxygen or enrichedair. An auxiliary fuel may be introduced to initiate the reaction or tosupply additional heat, as indicated by the 'dotted lines whichrepresent an optional procedure. Recycled SO: may also be introduced inStage A. In this stage partial roasting takes place, the sulphide orereacting with the oxygen with the formation of SO2. In Stage B which isshown just below Stage A, the temperature reaches the point at which thesuspended particles of ore fuse and these molten particles react withthe SO2 present to form sulphur and metal oxide. The suspended particlesand gases then enter the Stage C where the reaction is completed, thisstage being cooled, if desired, by the introduction of a cooling mediumwhich may be molten sulfur or water, for example, as indicated by thedotted lines. If a. cooling medium is employed, the metal oxide formedin the process is collected as a solid and may be passed directly to ametal recovery operation. In another embodiment, indicated on the flowsheet in dotted lines, the temperature in Stage C is maintained abovethe fusion point of the metal oxide which then falls to the bottom andis collected in the form of a molten bath. The molten bath may be passedto a purification step for the removal of sulphide impurities. The gasesrecovered in Stage C are passed to a sulphur recovery step and from thisstep SC may be recycled to Stage A, as indicated in dotted lines.

The reactions which occur in the process represented in Fig. 2 arethesame as those which have -been already described. But in this processthe suspended ore passes downwardly through a tower in counter-currentiiow to SO2-containing gases which are introduced at the bottom of thetower, as shown. In this process oxygen is introduced into the tower,preferably between Stages A and B, passing upwardly and 'serving toproduce SO2 by reaction with the ore. The SO: and sulphur formed in theprocess passes out at the top of the tower to a sulphur recovery stepfrom which point SO: is passed to a recovery step, part being recycledto the bottom of the tower,

as indicated in the figure. The metal oxide which falls to the bottom ofthe tower is passed to a metal recovery step.

- The invention will be more fully described in thefollowing with`reference to some examples o f applications thereof.

First those forms of the invention will be described in which thesulphide material is led in parallel flow with the oxidizing gas. andfor the sake of simplicity it is at first assumed that the sulphidematerial only contains sulphide of iron, e. g. pyrites or pyrrhotites.When the sulphide material is not present in a pulverulent state, itshould first be finely ground. Fiotationmaterials (e. g. fines) may as arule be used without further comminution, but if a very rapid andcomplete oxidation is desired, a further crushing of4 at least coarserparticles in the flotation material may be advisable. If the sulphidematerial contains an appreciable amount of moisture, it should be driedbefore The distribution of the sulphide material in the oxidizing gasstream may be eected by mechanical or pneumatical means, the lattermethod being generally preferred. The whole or part of the oxidizing gasis preferably employed as a means of obtaining the pneumatic action andthe distribution is effected in substantially the same manner as in thecase of heating with pulverized fuel. In

order to effect or promote the initiation of the oxidation process someother more inflammable substance, such as fuel oil, powdered coal, sul--phur, producer or natural gas, gas containing carbon monoxide, etc., maybe injected together with the sulphide material into the gas stream, soas to produce suiilcient heat, after ignition, to start the oxidationprocess proper. When using oxygen of air highly enriched with oxygen,the additional combustibles will generate a higher temperature thanwould otherwise be the case.

At the same time the advantage is obtained, that such gas richer inoxygen will cause the oxidation of the sulphide material to begin at alower temperature than when the oxidation is carried out by means ofair.f A strong preheating of all or part of the oxidation gas as well asof the sulphide material will facilitate the starting of the oxidationprocess.

The stream of gas is now, by aforesaid means, given a temperature atleast corresponding to I ing of the oxidized sulphide material.

As mentioned above, the roasting may be carried out in such a way that amelting of the metallic oxides formed will take place during theoxidation process. In connection therewith, the molten particles presentin the gas stream are, according to one mode of procedure of the-inventlon, completely or partly separated from this in the form of amolten bath. In the oxidation of materials wholly or substantiallyconsisting of sulphides of iron, these particles will, besides apossibly remaining content of sulphide, wholly or substantially consistof oxides of iron. l,Since the oxides of iron have a comparatively highmelting point, it is, in the case of such a mode of procedure of theinvention, important to impart such a high temperature to the gas streamthat it will have a melting and not coolingaction on unmelted ironoxide. It is therefore preferred to use oxygen or air highly enrichedwith oxygen as al means of oxidation. In this way it is possible t0obtain a low velocity of the gas stream, which is important for theseparation of the particles in the form of a molten bath. The processmay be carried out in a reverberatory furnace, "ash roaster or the liketo which the sulphide material is supplied -by the a-id of oxygenthrough jet burners, in which case an easily igniting material which issupplied for a starting up of the combustion, e. g. powdered coal, maybe supplied through the same burner. Part of the oxygen may if desiredbe supplied outside the burner. After ignition, the sulphide particleswill rapidly become heated to such a temperature that a reaction takesplace between these and the oxygen. If the sulphide consists of pyrites,SO2 is first formed, which diiuses in the gas and causes its temperatureto rise rapidly, while the particles of pyrite, owing to the sulphurwhich evaporates from their interior will become heated somewl t slower.If the sulphide consists of FeS, a simu.- taneous formation of SO2 andiron oxide will chiefly take place. As soon as the iron sulphide beginsto melt, the SO2 will also be able to a large extent to react with theiron sulphide with the formation of oxide of iron and free gaseoussulphur. By regulating the supply of oxygen, it is thus possibleaccording to the result desired, to carry out the oxidation processunder such conditions that either all or practically a-ll sulphur willbe 'transformed into SO2, or else so that at least a considerablepercentage of the sulphur originally combined as sulphides will berecovered in the form of free sulphur. If the process is to be carriedout in such a way that a high sulphur content is obtained in theresultant gas, an extra supply of heat is generally required toaccomplish the reaction; in such cases a larger quantity of additionalcombusti-bles in the form of powdered coal, oil or the like, istherefore supplied, than when the chief aim of these additions is simplythe starting up of the oxidation process. A preheating of the oxidationgas and the pyrites is also in such cases to be recommended. Oxygenshould furthermore in this case be used as oxidation gas.

As already mentioned the separation of the oxidized sulphide particlesin the form of a molten bath may be facilitated by the simultaneous useof a gas rich in oxygen and by a combustion to SO2.,l of sulphurliberated from the sulphide material by means of a/regulation of theoxygen supply, instead of 'recovering the sulphur in a free s-tate. Theoxygen content of the supplied oxidizing gas should in such cases be atleast twice that of ordinary air and preferably still higher. When ahigh melting temperature is required or when-\the sulphide material hasa high content of gangue, practically pure oxygen gas is preferablyemployed as oxidizing gas. Excess of oxidizing gas should as a rule beavoided. The

quantity of free Aoxygen added should preferably `be adjusted in suchmanner," that it will be completely or practically completely consumed.This will make the amount of gas smaller and formation of S03 will beavoided. In certain cases. particularly when as complete an oxidation ofthe sulphur in .the sulphide material as possible is desired, it isadvisable to supply an excess of oxygen; in this case the content offree oxygen in the exit gas, however, should preferably not be allowedto rise higher than to correspond to less than half the content of SO2in the exit gas computed on a volume base. and the oxygen content of thesupplied gas stream are generally adjusted so that the SO2-content ofthe exit gas will exceed 1A, 4by volume of the gas; the Soz-contentpreferably being kept between 50 and 100 per cent by volume. It ishowever possible, particularly if the suspended particles are of not toosmall grain size,v to permit the SO2-content of the waste gases to sinkto 25'per cent by volume. It is suitable, also in such cases when theroasting is conducted in such a manner, that a considerable formation offree sulphur takes place, to adjust the percentage of oxygen in theoxidizing gas in such manner that the exit gas, after the sulphur hasbeen separated off, will contain at least 25 per cent by volume of SO2.If it is desired to conduct the oxidation process in such a way that aparticularly high con-tent of S02 is obtained in the exit gas, e. g.'T5-100 per cent, and if by using oxygen or air highly enriched withoxygen the reaction temperature obtained will become higher than wouldbe desirable, it is possible, instead of using air less rich in oxygen,thus obtaining a lower SO2-content than desired, to dilute the oxidizinggas by returning part of the exit gas or SO2 recovered from this gas. Y

The richer the employed oxygen containing gas is, the smaller will bethe volume of gas and the easier the precipitation of the oxidizedsulphide particles in the form of a molten bath at the bottom of thefurnace. To facilitate the separation, the jet burners are preferablydirected downwards obliquely or at right angles to the molten bath. Suchmeasures should as a rule be taken that the particles will have totravel a comparatively long distance before striking the molten bath; itis also advisable to let the gas stream with its suspended particlesmake a fairly sharp turn in the furnace. It is e. g. possible to directthe gas stream containing the particles, towards a rear wall of thefurnace or against the molten bath near this rear wall, and to let thegas stream turn and sweep over the surface of the molten bath, and thenremove it from the furnace on the same side as the burners are located,e. g. at some point below these latter. The molten iron oxide bath ispreferably tapped at certain intervals. It is in this case advisable tosubject it, directly from its state of fusion, to a granulation, e. g.by means of air, to effect The oxidation process* an oxidation of ironsulphide which may be mechanically mixed with or dissolved in the bath.As an alternative or inc'onnection herewith, the bath may, aftercooling, besubiected to a sintering. If, on the other hand, the ironnoxide bath also contains more valuable sulphides. e. g. of copper ornickel, it is advisable to let the bath slowly solidify and, aftercrushing to a finely divided state, subject it to notation. If thesulphide material contains a considerable amount of gangue, the moltenbath will, besides oxide of iron, also contain a considerable amount ofother constituents such as silica. Since for this reason, it will beless suited asa raw material for the production of iron, it is as a ruleadvisable in such cases to disregard its use for this purpose andinstead to adjust the composition of the slag by means of slag-producingadditions, so that unreacted (non-oxidized) sulphide is more easilyseparated out in the form of matte. In many cases, when a material witha high content of sulphide is used, it is also advisable to reduce themelting-point of the slag by means of slagproducing additions. This isi. af made in order to overcome the difiiculty of obtaining a refractorylining in the furnace which is not strongly attacked by slag rich iniron oxide. It is also possible to considerably reducejhe heat lossesdue to radiation if the melting-point of the slag is lowered. 'I'heslag-producing additions may consist of quartz, lime, iluorspar, etc.,and may be directly added to the molten bath or else wholly or in partsupplied in powder form disum, owing to the formation of silicate. isdis-- placed in favour of the formation of sulphur. If the sulphidicmaterial besides sulphides of iron, also contains a considerable amountof sulphides of other metals such as copper or nickel, it is advisableto adjust the process of roasting in such a way that an incompleteoxidation of iron sulphide will take place, in which case these othersulphides will chieily enter as constituents in a matte which collectsbelow the slag bath. When an incomplete oxidation of the sulphidematerial is desired, the length of the path which the sulphide materialhas to travel to reach the molten bath may be made shorter than in othercases. When this matte has a comparatively high content of ironsulphide, an enrichment of the more valuable components such as copper,nickel and precious metals, may be obtained by crushing the matte andsubjecting it in above described manner to an incomplete roasting incombination with smelting. The main part of its content of iron sulphidewill by this treatment become oxidized and. together with possiblysupplied slag-producing additions enter into the slag, whereas theremaining sulphides will i'orm a matte.

If at a given reaction temperature, a reaction is possible betweenmetallic sulphide and metallic oxide, formed by the oxidation of theformer, with lthe formation of metal and SO2, the process may beadjusted in such a way, that the roasting will take place with theformation of metal. This will e. g. be the case when roasting materialscontaining copper sulphide. By regulating the supply of oxygen it isthus according to process possible to recover copper matte in the formof molten copper. In this case the oxidizing gas consists of engen orhighly oxygen-enriched air and the quantity of oxygen should preferablybe adjusted, so that it will be sufficient to convert the whole quantityof sulphur combined with the copper to SO2. Mattes which. in addition tocopper. contain other metals may also be roasted according to theprocess with the formation of free copper. Materials rich in leadsulphide, such as galena, may according to the invention be treatedsimilarly to copper sulphide in such a manner that lead is liberated andseparated in a molten state.

If the sulphide material at the same time contains sulphides which arecomparatively diiilcult to volatilize, e. g. sulphides of iron, copper,nickel, and components which are or, during oxidation, will give rise tomore volatile products, such as compounds of arsenic, the process may becarried out in such a way that the non-gaseous oxidation products of thesulphides difficult to volatilize are, at least to a large extent,separated in the form of a molten bath, while the more volatile productswill be separated from the gas during a later stage. If, according tomodes of procedure described below, the non-gaseous oxidation productsof the sulphides are separated in a pulverulent state instead of in theform of a molten bath, it is advisable to separate at least the majorpart of the pulverulent oxidation products from the gas at such a hightemperature, that the compounds of arsenic will still remain in agaseous state. If the gas contains a considerable amount of free sulphurthe compounds of arsenic will be obtained in the form of sulphide uponseparation from the gas. If a sufficient amount of oxygen is present inthe gas arsenic oxide will, however, form.

Instead of separating particles from the gas stream at such a hightemperature that a molten bath is formed, it is according to a mode ofprocedure of the invention, possible to separate the roasted particlesin a pulverulent state. In this case the temperature conditions arepreferably regulated during the roasting in such a way, that no meltingof the oxides of iron formed during the roasting will take place. Thisprocedure may preferably be carried out in such a way, that the sulphidematerial and the oxidizing gas are supplied in the upper part of a hightower, e. g.

.by means of jet burners, and allowed to move downwardly in parallel ow,the oxidation process being started by means of easily lgniting fueladditions. Alternatively, use may be made of an upward movement of thegas and the sulphide material, in which case the sectional area of thetower should be adjusted, in relation to the desired total amount of gasper unit of time, in such a manner that the velocity of the gas willsuiiice for carrying with it the sulphide particles. Coarser particles,in the case of an otherwise upward directed iiow, may, if desired, beintroduced at the top of the tower and be allowed to sink through thestream and are in this case withdrawn from the base of the tower. Ifthese particles have not been completely roasted during their downwardmovement, an after-roasting pletely or chiey consisting of sulphides ofiron, aq'ueous solutions, it is possible, by adjusting the suitable toemploy the last mentioned process for 'the roasting in a vertical towerin combination with such a mode of roasting that at least a considerableamount of the sulphur will separate out in the form of free sulphur. Ithas, in fact, been found that, apart from the use of an extremely hightemperature, the most favourable temperature range for a reactionbetween SO2 and iron sulphide with the formation of iron oxide and freesulphur is precisely limited, downwards by the melting point of ironsulphide and upwards by the melting of iron oxide. this temperaturerange yields of more than 90 per cent of the sulphur from the sulphidehave been obtained in the form of free sulphur, whereas immediatelybelow the melting point of iron sulphide only a slight formation of freesulphur has been ',demonstrated. Enriched air with a high oxygen contentis preferably used as an oxidation gas, since this i. e. has theadvantage that the particles, after the treatment in the tower, may bemore easily separated and the condensation of the sulphur highlyfacilitated. In certain cases it is however possible to use a gas poorerin Oxygen, or an oxygen gas diluted with water vapour or SO2. Toregulate the temperature it is thus possible to inject water orintroduce SO2-gas into those parts of the tower where the temperaturehas a tendency to become too high. In lthose parts of the tower wherethe reaction has proceeded to such extent that no free oxygen isavallable, the temperature will show a tendency to sink; by supplyingoxygen to these parts it is possible again to increase or maintain thetemperature. If desired, the temperature may, at the beginning of thereaction process, be allowed to exceedthe melting point of the ironoxides, but should in this case, after the free oxygen has beenconsumed, be reduced below said temperature. When employing such atreatment in a tower it is as an alternative also possible to conductthe process in such a manner that the sulphur of the sulphides willcompletely or chiey become oxidized to SO2.

A rapid cooling of the gas stream with the* particles suspended in it,from a temperature exceeding the melting point-of iron sulphide down tosuch a temperature that a re-forming of sulphide by a reaction betweensulphur and iron oxide is as far as possible prevented, is advisable insuch cases, when it is desired to recover sulphur in a free state. Ifdesired 'the particles may as an alternative, wholly or in part, beseparated from the gas stream, e. g. in settling chambers, before thetemperature of the gas stream has reached a level below the meltingpoint of the iron sulphide. A rapid cooling may be effected by injectionof solid or uid sulphur or by means of water. The cooling is preferablynot accomplished until the gas stream has left the tower. When the gasand the sulphide material are supplied at the top of the tower and movedownwardly, the cooling may, as an alternative, 4oe effected byinjecting the cooling media into the lower part of the tower. If wateris used as a cooling medium, the quantity of water may be adjusted sothat the sulphur contained in the gas will also condense and be removedwith the water or with the water vapour formed, in which latter case itis recovered by a condensation of this latter. If the sulphur is removedwith the water together with the roasted sulphide material, it is, ifnecessary, possible to separate it by a flotation process. If thecooling is effected by means of Within quantity of solution, to utilizethe sensible heat of the gas stream and its particles, for concentratingthe solution by vaporization. Sea water may e. g. be evaporated by aldof waste heat of this kind for the recovery of salts dissolved in thewater.

If the cooling is effected by sulphur or a quantity of water adjusted insuch a way, that the gas still contains all or a substantial part of thesulphur in the form of vapour, the solid particles are separated fromthe gas, e. g. in settling chambers or by Cottrell precipitation, beforethe gaseous sulphur is condensed. The sulphur is then condensed out, theheat of condensation preferably being utilized for the production ofsteam. It is in this case suitable to employ coolers in -which theproduction of steam is effected at such \a pressure that the temperatureof the cooling tubes is kept either below 160 C., e. g. at about 125 C.,or else above 250 C., for the purpose of preventing the separation ofsulphur in a viscous form. Particularly in such cases where the gas iscooled to a temperature above that at which condensation begins by meansof sulphur injected in the gas in solid or fluid form, it is advisableto eifect the condensation step-Wise, e. g. in two or three stages ineach of which the sulphur is partially condensed. y In the case of athree procedure itis suitable to collect the first condensed sulphur,containing the largest quantity of impurities, separately, and tosubject it toga special purifying process. The subsequently separatedfraction is utilized for cooling the gas, whereas the third fraction asa rule is of a marketable quality without any further treatment.

When copper sulphide forms par-t of the material which contains ironsulphide, and this material is subjected to a roasting in a toweraccording to the procedure described, for the purpose of recovering freesulphur, the roasted material will still contain the copper in the formof sulphide. The copper may therefore be recovered from the particlesseparated from the gas by means of a :dotation process. This alsoapplies for' some other sulphides, such as nickel sulphide. Magneticnickel sulphide ores and concentrates may therefore, especially if thenickel is present in the form of free pentlandite grains, after beingroasted for the recovery of sulphur according to the describedprocedure, with advantage be subjected to a treatment for the recoveryof nickel and copper. This may e. g. be done by flotation orchlorination, e. g. with gaseous chlorine, of the nickel sulphide and afollowing leaching. The chlorination process is to be preferred to aotation in the case of ores in which the nickel sullphide minerals areintimately associated with the magnetic sulphide minerals Roasting inconnection with the separation of the solid particles in a pulverulentstate may, if it is desired to obtain copper, nickel etc., also beeffected in such a manner, that a certain amount of iron sulphide willalso be contained in the roasted material, which latter may then besubjected to a smelting in a reverberatory furnace for a recovery of themore valuable metals in the form of components of a matte.

According to a further mode of procedure of the invention, it ispossible to recover sulphur by the roasting of materials containingsulphide of iron, while'these in a finely dividedr state are fallingcounter-currently to the oxidizing gas in a tower. From a thermal pointof view such a procedure offers great advantages. The procedure isparticularly applicable to the treatment of sulphide materials with nottoo high a content of extremely nely divided particles. 'Ihe preheatingand, in the case of pyrites, also the driving oil. of sulphur takesplace in the upper part of the tower. If this preheating and driving oifof sulphur should be effected exclusively by means of the sensible heatofthe gas stream, this would necessitate the use of a very largequantity of gas, which, in turn. would result in a 10W-sulphur contentin the exit gases. Supplemental heat is therefore preferably supplied tothe upper parts of the tower by combustion, e. g. by introducing oxygenat one or more points in the upper part of the tower for the combustionof sulphur, or by supplying combustible substances either separately orin combination with an oxygen containing gas, which substances willproduce heat by reaction with the SO2 present in the upper part of thetower or with the oxygen supplied. Such combustible substances may e. g.consist of powdered coal, fuel-oil, gas containing carbon monoxide,hydrocarbons, producer or natural gas, hydrogen, etc. If powdered coalis used, this should preferably be so flnely divided that it will notsink in the gas stream to any appreciable degree. It is also possible asan alternative to add powdered coal of such a grain size that the grainswill sing in the gas stream, but the powder should in such casespreferably be supplied from the uppermost part of the tower, e. g. inadmixture with the powdered sulphide material. This latter material ismechanically or pneumatically dispersed into the gas stream. In thelatter case the dispersing may be effected by means of a gas whichcontains e. g. carbon monoxide, and which may be utilized for convert--ing the SO2, forming part of the exit gas, to sulphur, or else byreturning part of the escaping gas, preferably after the sulphur hasbeen removed by condensation. For the purpose of temperature control inthe furnace, the major part of the oxygen is preferably introduced atdi'erent levels of the middle sections of the tower, whereas SO2-gas,with or without admixture of free oxygen, is preferably introduced atthe base of the tower. The SO2-gas is heated by the hot particles andwill, after having attained a suillciently high temperature, react withthe iron sulphide remaining in the grains. A content of free oxygen inthe SO2-gas will contribute to make the oxidation process more complete.A preheating of the SO2-gas will also help this to more rapidly attainthe temperature necessary for the reaction. A supply of SO2-gas at thebase of the tower will also contribute to a displacing of theequilibrium in the upper part of the tower in favour of the formation ofsulphur. Instead of adding SO2, or simultaneously with such addition, itis possible to supply water vapour, e. g. by spraying water on theparticles which have collected in the lower part of the tower. A mixtureof water vapour and oxygen may also be used to advantage. Instead ofoxygen it is possible to use either air enriched with oxygen or ordinaryair, although this will make it more diiiicult to recover sulphur andSO2 from the waste gases. Part of the sulphide material may instead ofbeing introduced at the top be introduced at lower levels of the tower.

'I'he roasted sulphide material withdrawn from the base of the tower maybe converted by sintering to a form suitable for its use as iron ore. Ifthe roasted sulphide material contains sulphides of copper, nickel,etc., it may be worked up for recovery of these metals, e. g. insubstantially the same manner as already described.

'I'he gasesl escaping from the tower are freed from entrained particles,e. g. in settling chambers. Volatile compounds of arsenic which maypossibly be present in the gas are condensed out and preferablyseparated od, before the condensation of sulphur takes place. Thecooling of the gas stream and separation of the sulphur content of thegas may be effected in substantially the same manner as described above.As, however, it is not necessary in the case of this procedure, to coolthe gas extremely rapidly. it is in this case possible as analternativeto carry out the ilrst part of the cooling with a view toutilizing the heat for the productionof steam. After the sulphur hasbeen condensed out, all or part of the residual gas may, if desired, bereturned directly to the base of the tower in the form of an SO:-containing gas. It is however, as a rule. advisable to remove otherconstituents, e. g. a possible nitrogen content, from that part of thegas which is to be re-circulated in the process, before the gas isreturned to the tower. 'I'his may be done by dissolving SO2 in water orother solvent and then expelling it from this. Even in cases, when theSO2-content of the gas is not, either wholly or in part, returned to theprocess, it is advisable to subject it to a purification, beforeutilizing it for the production of sulphur according to known methods orfor other purposes. Reducing agents for the SO2 may, if desired, besupplied to the gas immediately after it has left the tower and beforeit has been cooled down.

In certain cases it is advisable to divide the sulphide material intodifferent grain classes and to treat each of these separately, the mostilnely divided particles being preferably treated in a parallel ilow.

I claim:

1. A process for the production of sulphur from a sulphide ofiron-containing-material, comprising bringing said material in the formof ne particles in suspension in an SO: containing gas and regulatingthe composition of the gas and the temperature, so that the suspendedfine particles fuse and at least a considerable amount of sulphur isformed by the reaction, in the absence of free oxygen, between thesuspended molten sulphide and the SO2.

2. A process for the production of sulphur from a sulphide ofiron-containing-material, comprising oxidizing line particles of saidmaterial while in suspension in a stream of a gas originally containingfree oxygen, regulating the amount of said oxygen in said gas in suchmanner that only a part of the sulphur content of the sul"` phidematerial is oxidized to SO2, and, in order to produce sulphur,continuing the oxidation of sulphide of iron by means of SO2 at atemperature at which suspended sulphide particles are at least partly ina molten condition.

3.V A process for the production of sulphur from a sulphide ofiron-containing-material, comprising suspending and oxidizing fineparticles of the sulphide material in a stream of a gas, whichoriginally contains at least a considerably higher percentage of freeoxygen than ordinary air, reg-I ulating the amount of oxygen in said gasin such manner that said oxygen is suillcient to oxidize a part only ofthe sulphur content of the sulphide material to SO2, and, in order toproduce sulphur, continuing the oxidation of the suspended sulphide ofiron by means of SO2 at a temperature at which the suspended particlescontain sulphide of iron in a molten state.

4. A process for the production of sulphur from a sulphide ofiron-containing-material, comprising suspending and oxidizing neparticles of the sulphide material in a stream of a gas, originallycontaining at least a considerably higher content of free oxygen thanthat of ordinary air, initiating the oxidation by burning in the gas ofa material which ignites easier than the sulphide material, regulatingthe amount of free oxygen in said gas in such manner that said oxygen issufficient to oxidize a part only of the sulphur content of the sulphidematerial to SO2, and producing free gaseous sulphur by continuing theoxidation of the suspended sulphide of iron by means of SO2 at atemperature at which at least part of the iron sulphide content of thesuspended particles is in a molten state.

5 A process for the production of sulphur comprising suspending andoxidizing ne particles of.

a pyrite material in a stream of a gas, which originally at least mainlyconsists of free oxygen, regulating the oxidation, so that the freeoxygen is consumed when only part of the sulphur content of the pyriteis oxidized to SO2, continuing the oxidation by means of SO2 at atemperature at which at least part of the remaining suspended sulphideis in a molten condition, and regulating both steps of the oxidation sothat gaseous sulphur is formed during this latter oxidation in aquantity exceeding half the original sulphur content of the pyrite.

6. A process for the roasting and smelting of ne particles rich insulphide of iron, comprising suspending and roasting the sulphidematerial in a gas containing free oxygen, regulating the amount of freeoxygen so that only part ofthe sulphide of iron is oxidized to form SO2and regulating the temperature so that the oxidation continues byreaction between SO2 and sulphide of iron converted to a molten stateunder formation of gaseous sulphur and oxide of iron, at least partlyseparating the oxidized product from the gas while in a molten conditionunder the formation of a molten bath, said bath being at least partly inthe form of an oxide slag mainly consisting of oxide of iron and alsocontaining sulphides as impurities, tapping said oxide slag andgranulating the slag while in a fluid condition by treatment with anoxidizing gas, for the purpose of lowering the sulphur content of theslag.

7. A process for treating materials containing sulphide of iron and asulphide of at least one of the metals copper and nickel, comprisingsuspending the sulphide material in form of 'fine particles in anoxidizing gas originally containing free oxygen in amount substantiallygreater than that contained in air, and submitting the sulphide materialwhile in suspension to an incomplete roasting while regulating thetemperature so that the roasted particles will melt, and collecting atleast part of the oxide and the sulphide-containing particles whilestill in a molten condition into a molten bath, and regulating the slagforming components of the suspended material so that the oxide componentof the roasted particles collected in the bath will be rich in oxide ofiron, the volume of gas employed being substantially less than thatrequired when air is used in the process, whereby collection of theroasted particles is facilitated.

8. A process for roasting of sulphide material, mainly consisting of asulphide of at least one of the metals copper and lead, for the purposeof recovering the corresponding metals, comprising suspending andoxidizing the sulphide material in a nely divided form-in a stream oi agas, obtained by mixing a gas at least mainly consisting of free oxygenwith part of the resulting SO2-containing roasting gas, regulating theoxidation so that formation of SO2 and molten metal takes place, andcollecting at least part oi the suspended material while in a moltencondition in the form of a molten bath.

9. A process for producing sulphur from sulphide ofiron-containing-material, comprising suspending the sulphide material inthe form of iine particles in a stream of an oxidizing gas, whichoriginally has a considerably higher content of free oxygen than that ofair, regulating the amount of free oxygen and the development of heat sothat the free oxygen will be consumed to form SO2 while producing anincomplete oxidation of the sulphide material, continuing the oxidationof sulphide of iron by means of SO2 to form elementary gaseous sulphurat a temperature maintained sufficiently high to keep the iron sulphidein a molten state but below the melting point of oxide of iron.

10. A process for producing sulphur, comprising suspending ne particlesof a sulphide of iron-containing-material in a stream of a gasoriginally containing free oxygen, roasting the suspended material whileat least mainly conducting the gas and the sulphide particles inparallel ow, regulating the total amount of free oxygen and thedevelopment of heat so that the oxygen is consumed to form SO2 whileonly incompletely oxidizing the sulphide material, and so that oxidationof sulphide of iron will continue by means of SO2 at a temperature atwhich said sulphide is in a molten condition; and thereafter lsuddenlycooling to such a temperature, that no considerable :je-formation ofsulphide of iron will occur.

11. A process for producing sulphur, comprising suspending ne particlesof a sulphide of iron-containing-material in a stream of a gasoriginally containing free oxygen, roasting the suspended material Whileat least mainly conducting the gas, and the sulphide particles inparallel ilow, regulating the total amount of free oxygen and thedevelopment of heat so that the oxygen is consumed to form SO2 in anincomplete oxidation of the sulphide material; continuing the oxidationof sulphide of iron by means of SO2 at a temperature at which saidsulphide is in a molten state, and thereafter cooling the resultinggases by contact with sulphur.

12. A process for producing sulphur, comprising suspending fineparticles of a sulphide of iron-containing-material in a stream of a gasoriginally containing free oxygen, roasting the suspended material whileat least mainly conducting the gas and the sulphide particles inparallel ilow, regulating the total amount of free oxygen and thedevelopment of heat so that the oxygen is consumed to form SO2 whileonly incompletely oxidizing the sulphide material; and continuingoxidation of the sulphide of iron by means of SO2 at a temperature atwhich said sulphide is in a molten state, and thereafter coolingdirectly by contact with water.

13. A process for roasting sulphide of ironcontaining-materialscomprising heating and oxidizing the sulphide material while in the formof line particles falling in a tower against an upwardly directed ow ofa gas, introducing a stream of a gas rich in SO: in the lower part ofthe tower and mixing said gas, at least at one level of the tower, witha gas mainly consisting of free oxygen, the temperature in at least onepart of said tower being maintained above the melting point of ironsulphide.

14. A process for roasting and smelting comprising suspending ilnelydivided particles of an iron sulphide-containing ore in a gas originallycontaining free oxygen in amount substantially 10 greater than thatcontained in air, heating the

